我如何在c#中生成一个随机的8个字符的字母数字字符串?
当前回答
Eric J.写的代码很潦草(很明显这是6年前写的……他今天可能不会写那个代码)，甚至还有一些问题。
与目前提出的一些替代方案不同，这个方案在密码学上是合理的。
不真实的…在密码中有一个偏差(正如在注释中所写的那样)，bcdefgh比其他的更有可能(a不是，因为通过GetNonZeroBytes，它不会生成值为0的字节，因此a的偏差由它平衡)，所以它在密码学上并不可靠。
这应该可以纠正所有的问题。
public static string GetUniqueKey(int size = 6, string chars = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890")
{
using (var crypto = new RNGCryptoServiceProvider())
{
var data = new byte[size];
// If chars.Length isn't a power of 2 then there is a bias if
// we simply use the modulus operator. The first characters of
// chars will be more probable than the last ones.
// buffer used if we encounter an unusable random byte. We will
// regenerate it in this buffer
byte[] smallBuffer = null;
// Maximum random number that can be used without introducing a
// bias
int maxRandom = byte.MaxValue - ((byte.MaxValue + 1) % chars.Length);
crypto.GetBytes(data);
var result = new char[size];
for (int i = 0; i < size; i++)
{
byte v = data[i];
while (v > maxRandom)
{
if (smallBuffer == null)
{
smallBuffer = new byte[1];
}
crypto.GetBytes(smallBuffer);
v = smallBuffer[0];
}
result[i] = chars[v % chars.Length];
}
return new string(result);
}
}
其他回答
非常简单的解决方案。它使用ASCII值，只是在它们之间生成“随机”字符。
public static class UsernameTools
{
public static string GenerateRandomUsername(int length = 10)
{
Random random = new Random();
StringBuilder sbuilder = new StringBuilder();
for (int x = 0; x < length; ++x)
{
sbuilder.Append((char)random.Next(33, 126));
}
return sbuilder.ToString();
}
}
在这个线程中只是一些不同答案的性能比较:
方法与设置
// what's available
public static string possibleChars = "abcdefghijklmnopqrstuvwxyz";
// optimized (?) what's available
public static char[] possibleCharsArray = possibleChars.ToCharArray();
// optimized (precalculated) count
public static int possibleCharsAvailable = possibleChars.Length;
// shared randomization thingy
public static Random random = new Random();
// http://stackoverflow.com/a/1344242/1037948
public string LinqIsTheNewBlack(int num) {
return new string(
Enumerable.Repeat(possibleCharsArray, num)
.Select(s => s[random.Next(s.Length)])
.ToArray());
}
// http://stackoverflow.com/a/1344258/1037948
public string ForLoop(int num) {
var result = new char[num];
while(num-- > 0) {
result[num] = possibleCharsArray[random.Next(possibleCharsAvailable)];
}
return new string(result);
}
public string ForLoopNonOptimized(int num) {
var result = new char[num];
while(num-- > 0) {
result[num] = possibleChars[random.Next(possibleChars.Length)];
}
return new string(result);
}
public string Repeat(int num) {
return new string(new char[num].Select(o => possibleCharsArray[random.Next(possibleCharsAvailable)]).ToArray());
}
// http://stackoverflow.com/a/1518495/1037948
public string GenerateRandomString(int num) {
var rBytes = new byte[num];
random.NextBytes(rBytes);
var rName = new char[num];
while(num-- > 0)
rName[num] = possibleCharsArray[rBytes[num] % possibleCharsAvailable];
return new string(rName);
}
//SecureFastRandom - or SolidSwiftRandom
static string GenerateRandomString(int Length) //Configurable output string length
{
byte[] rBytes = new byte[Length];
char[] rName = new char[Length];
SolidSwiftRandom.GetNextBytesWithMax(rBytes, biasZone);
for (var i = 0; i < Length; i++)
{
rName[i] = charSet[rBytes[i] % charSet.Length];
}
return new string(rName);
}
结果
在LinqPad中测试。对于长度为10的字符串，生成:
from Linq = chdgmevhcy [10] from Loop = gtnoaryhxr [10] from Select = rsndbztyby [10] from GenerateRandomString = owyefjjakj [10] from securefastrrandom = VzougLYHYP [10] from securefastrrandom - nocache = oVQXNGmO1S [10]
性能数据会有细微的变化，偶尔NonOptimized会更快，有时ForLoop和GenerateRandomString会切换谁领先。
LinqIsTheNewBlack (10000x) = 96762 ticks elapsed (9.6762 ms) ForLoop (10000x) = 28970滴答流逝(2.897毫秒) ForLoopNonOptimized (10000x) = 33336滴答流逝(3.3336毫秒) 重复(10000x) = 78547滴答流逝(7.8547毫秒) GenerateRandomString (10000x) = 27416 tick elapsed (2.7416 ms) securefastrrandom (10000x) = 13176滴答流逝(5ms)最低[不同的机器] securefastrrandom - nocache (10000x) = 39541 ticks elapsed (17ms) low[不同的机器]
对于加密和非加密，有效地:
public static string GenerateRandomString(int length, string charset = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890") =>
new Random().GenerateRandomString(length, charset);
public static string GenerateRandomString(this Random random, int length, string charset = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890") =>
RandomString(random.NextBytes, length, charset.ToCharArray());
public static string GenerateRandomCryptoString(int length, string charset = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890")
{
using (var crypto = new System.Security.Cryptography.RNGCryptoServiceProvider())
return crypto.GenerateRandomCryptoString(length, charset);
}
public static string GenerateRandomCryptoString(this RNGCryptoServiceProvider random, int length, string charset = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890") =>
RandomString(random.GetBytes, length, charset.ToCharArray());
private static string RandomString(Action<byte[]> fillRandomBuffer, int length, char[] charset)
{
if (length < 0)
throw new ArgumentOutOfRangeException(nameof(length), $"{nameof(length)} must be greater or equal to 0");
if (charset is null)
throw new ArgumentNullException(nameof(charset));
if (charset.Length == 0)
throw new ArgumentException($"{nameof(charset)} must contain at least 1 character", nameof(charset));
var maxIdx = charset.Length;
var chars = new char[length];
var randomBuffer = new byte[length * 4];
fillRandomBuffer(randomBuffer);
for (var i = 0; i < length; i++)
chars[i] = charset[BitConverter.ToUInt32(randomBuffer, i * 4) % maxIdx];
return new string(chars);
}
使用生成器和LINQ。不是最快的选项(特别是因为它不会一次生成所有字节)，但相当整洁和可扩展:
private static readonly Random _random = new Random();
public static string GenerateRandomString(int length, string charset = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890") =>
new string(_random.GetGenerator().RandomChars(charset.ToCharArray()).Take(length).ToArray());
public static string GenerateRandomCryptoString(int length, string charset = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890")
{
using (var crypto = new System.Security.Cryptography.RNGCryptoServiceProvider())
return new string(crypto.GetGenerator().RandomChars(charset.ToCharArray()).Take(length).ToArray());
}
public static IEnumerable<char> RandomChars(this Func<uint, IEnumerable<uint>> randomGenerator, char[] charset)
{
if (charset is null)
throw new ArgumentNullException(nameof(charset));
if (charset.Length == 0)
throw new ArgumentException($"{nameof(charset)} must contain at least 1 character", nameof(charset));
return randomGenerator((uint)charset.Length).Select(r => charset[r]);
}
public static Func<uint, IEnumerable<uint>> GetGenerator(this Random random)
{
if (random is null)
throw new ArgumentNullException(nameof(random));
return GeneratorFunc_Inner;
IEnumerable<uint> GeneratorFunc_Inner(uint maxValue)
{
if (maxValue > int.MaxValue)
throw new ArgumentOutOfRangeException(nameof(maxValue));
return Generator_Inner();
IEnumerable<uint> Generator_Inner()
{
var randomBytes = new byte[4];
while (true)
{
random.NextBytes(randomBytes);
yield return BitConverter.ToUInt32(randomBytes, 0) % maxValue;
}
}
}
}
public static Func<uint, IEnumerable<uint>> GetGenerator(this System.Security.Cryptography.RNGCryptoServiceProvider random)
{
if (random is null)
throw new ArgumentNullException(nameof(random));
return Generator_Inner;
IEnumerable<uint> Generator_Inner(uint maxValue)
{
var randomBytes = new byte[4];
while (true)
{
random.GetBytes(randomBytes);
yield return BitConverter.ToUInt32(randomBytes, 0) % maxValue;
}
}
}
一个更简单的版本，使用LINQ只用于非加密字符串:
private static readonly Random _random = new Random();
public static string RandomString(int length, string charset = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890") =>
new string(_random.GenerateChars(charset).Take(length).ToArray());
public static IEnumerable<char> GenerateChars(this Random random, string charset)
{
if (charset is null) throw new ArgumentNullException(nameof(charset));
if (charset.Length == 0) throw new ArgumentException($"{nameof(charset)} must contain at least 1 character", nameof(charset));
return random.Generator(charset.Length).Select(r => charset[r]);
}
public static IEnumerable<int> Generator(this Random random, int maxValue)
{
if (random is null) throw new ArgumentNullException(nameof(random));
return Generator_Inner();
IEnumerable<int> Generator_Inner() { while (true) yield return random.Next(maxValue); }
}
我听说LINQ是新的黑色，所以下面是我使用LINQ的尝试:
private static Random random = new Random();
public static string RandomString(int length)
{
const string chars = "ABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789";
return new string(Enumerable.Repeat(chars, length)
.Select(s => s[random.Next(s.Length)]).ToArray());
}
(注意:Random类的使用使得它不适用于任何与安全性相关的事情，比如创建密码或令牌。如果你需要强随机数生成器，请使用RNGCryptoServiceProvider类。)
一个包含所有字母字符和数字的解决方案，你可以随心所欲地更改:
public static string RandomString(int length)
{
Random rand = new Random();
string charbase = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789";
return new string(Enumerable.Range(0,length)
.Select(_ => charbase[rand.Next(charbase.Length)])
.ToArray());
}
如果你喜欢单行方法;)
public static Random rand = new Random();
public const string charbase = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789";
public static string RandomString(int length) =>
new string(Enumerable.Range(0,length).Select(_ => charbase[rand.Next(charbase.Length)]).ToArray());
